Buyer Not Making Payments on a Seller Financed House

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I bought a property in IL few months ago which I sold it to another buyer on seller financing (AKA Contract for Deed).

The seller is going through some sort of financial issues and is not able to make this months mortgage payment.
On further looking into the details, I found out that he has also not paid any association fees since last few months and now this months water bill is due as well.

What should I do at this time to take control this situation to get worse and reduce my loss ?